>
> David Gould wrote:
>
> [snip]
> > Here is the Spinlock back off patch I promised. This does semi-random
> > backoff using select() to lessen throughput degradation due to spinlock
> > contention with large numbers of runnable backends.
>
> Does this actually use some sort of random number generator? I'm
> thinking that this may not be entirely necessary. With Ethernet, this
> is needed to avoid another colission, but with locks, one process is
> guaranteed to get a lock.
>From the patch. Looks very good to me.
! * Each time we busy spin we select the next element of this array as the
! * number of microseconds to wait. This accomplishes pseudo random back-off.
! * Values are not critical and are weighted to the low end of the range. They
! * were chosen to work even with different select() timer resolutions on
! * different platforms.
! * note: total time to cycle through all 16 entries might be about .1 second.
! */
! int s_spincycle[S_NSPINCYCLE] =
! {0, 0, 0, 1000, 5000, 0, 10000, 3000,
! 0, 10000, 0, 15000, 9000, 21000, 6000, 30000
! };
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